The present invention relates to apparatus for opening and closing mold sections, and in particular to injection molding presses.
Liquid reaction molding or reaction injection molding (R.I.M.) is used in the formation of a wide variety of products. Such molding techniques utilize a molding press that opens and closes the mating mold sections and maintains a substantial closing pressure during the molding process. Typically these molding presses include a vertical C-shaped frame that is seated on a support bed. A pair of opposed platens are mounted on the upper and lower horizontal legs of the frame and the mating mold sections are mounted on these platens to be vertically aligned or stacked when closed. To close the mold sections the platens are first oriented with the mold mounting faces generally parallel to each other and then one or both of the platens are advanced toward the other.
In order to provide access to the inside of the mold after the platens have separated, one or both of the platens are pivoted (referred to as booking) in order to swing the mold sections to the side of the frame. Since the two platens are aligned vertically, the platen or platens pivot in a single vertical plane about two spaced horizontal axes. In presses that book a single platen, typically the upper platen is booked outwardly while the lower platen remains stationary forming an upwardly facing platform.
Heretofore, due to the vertical arrangement of the platens on such R.I.M presses an operator has been required to reach or stand under the upper platen and mold section to remove the molded part or otherwise service either platen. With mold closing presses having a stationary lower platen, the operator is required to reach into the path of travel of the closing mold in order to access the lower mold section. This overhanging arrangement presents a potential safety hazard to the operator, as well as presenting difficulties in accessing both mold sections. Since the platens are vertically spaced, when open both mold sections cannot be readily accessible to the operator unless the mold closing press is relatively small. If the lower platen is located at a convenient waist height for the operator, the upper platen necessarily must be raised to a height dictated by the maximum mold section size, and will be located overhead.
Further, the vertical arrangement of the platens and mold closing apparatus limit the maximum weight of the molds serviceable by such presses. Since the vertical framework must support the upper mold section, the platen and the pivoting apparatus all raised above the lower platen, the maximum mold weight that such machine can handle is limited. This is particularly true since the C-shaped frame supports the mold section, platen and pivoting apparatus in a cantilever fashion on the overhanging section of the frame. Typically, such mold presses cannot handle mold sections that weigh in excess of about fifteen tons per mold section.
Although mold closing apparatus of different types having platens that pivot about vertical axes have been used for relatively small molding applications, these mold closing devices are substantially different from injection molding presses that provide linearly converging platens which generate very large closing pressures. These prior mold closing apparatus require that an operator reach into the platen's pivotal closing path of travel in order to access the mold sections.